Process for cracking gasoline



Feb.. R5, 1938. D. G. BRANDT PROCESS FOR CRCKING GASOLINE Filed Juney 22,. 1932 2 Sheets-Sheet 1 D. G. BRANDT Feb. 15, 1938.

PROCESS FOR CRACKING GASOLINE- Fiized June 22, 1932 2 Sheets-Sheet 2 @www : INVENTOR AVID G. BRANDT 'l t TToRNEY Patented Feb. l5, '1 938 UNITED STATES PATET GFFICE David G. Brandt, Westfield, N. J., assigner to Power Patents Company, Hillside, N. J., a corporation of Maine Application June 22, 1932, Serial No. 618,623

5 Claims.

This invention re-lates to a process for producing anti-knock gasolines or motor fuels from straight run gasolines, -naphtha or knocking motor fuel distillates.

The improvement of gasolines with respect to their knocking tendencies has been proposed in the British patent to Detering No. 349,812 which refers to the cracking of straight run gasoline. This patent however discloses only a general prolO cedure and does not include important details which have been found of considerable advantage in the process of the present invention. The process of the present invention therefore constitutes an improvement in processes for increasl 5 ing the anti-knock properties of gasoline in which provision is made for an effective transformation of .knocking gasolines into anti-knock motor fuels. The invention has for its primary object the provision of a process and apparatus in which -20 knocking gasolines such as straight run gasolines ,may be transformed into more useful products for the type of internal combustion engines now in use.

A further object of the invention is the provision of a combined process for the transformation of knocking gasolines into anti-knock gasolines, and the cracking of heavy hydrocarbons for the production of a composite anti-knock motor fuel product.

With these objects in View the features of the invention will be described in detail in connection with the accompanying drawings in which:

Figure 1 is a diagrammatic representation of an apparatus particularly adapted for carrying out the process of the invention.

Figure 2 is an enlarged sectional view taken on the line 2 2 of Fig. 1 showing the furnace combustion tunnels and the ue gas discharge passage.

Figure 3 is a diagrammatic view of an apparatus similar to that of Fig. l showing a modified form of the invention.

In the drawings, similar apparatus elements in the different gures are referred to by the same reference numerals.

Referring to the modification shown in Fig. l, the straight run gasoline or naphtha to be cracked is introduced into the system through a feed pipe 2 and pump 4. This material introduced by the pump 4 is forced under a pressure of about 1000 pounds per square inch through heat exchangers 6 and 8 by means of connecting pipes I!! and I2. From the last heat exchanger 8 the preheated material which has now been heated up to a temperature of about 600 F. is passed through a pipe I4 and connecting pipe I5 into heating coils mounted in pipe still furnace I8. In passing through the pipe still furnace I8, the naphtha charging stock is heated to a cracking temperature of from 925 t0, 1100" E. and

a e) i) then discharged through pipes 20 and .22 directly into the upper portion of an enlarged chamber 24 through which the vapors pass downwardly and `discharge through one of the pipes 2B into the lower portion of a second cracking chamber 28 in which a small body of oil is maintained. IThe vapors are distributed into the body of oil by means of .a distributor flange or apron 3i? so that the charge of oil is uniformly heated and agitated by the high temperature vapors.

Since the products discharged from the pipe still furnace are at a substantially high temperature, it has been found advisable to reduce this temperature to a substantially lower point. For this purpose a high boiling point distillate is conducted through a line 32 and may be mixed directly with the highly heated products in pipe 22 or may be introduced into the lower portion of chamber 24 through a valved pipe 34. `Preferably about 90% of the quenching oil is introduced through the pipe 34. Under some circumstances the temperature of the vapors introduced into chamber l2li may be so high that the body of oil therein will be substantially va- ,porized Therefore, provision is made for introducing oil from the pipe 32 directly into the upper portion of chamber 28.

The temperature in chamber 28 is preferably maintained sufficiently high to cause substantial conversion of the oil therein. For example, a temperature of from 750 to 825 F. may be maintained.

Provision is made for the withdrawal of residue from chamber 28 through withdrawal line Y36 which may connect at various points to the lower 30 change substantially reduces the temperature of the vapors and effects condensation of certain of the higher boiling constituents. As shown in the drawings, two fractions of condensate are collected from heat exchanger il, one fraction being a relatively high boiling point material having a higher carbon residue than the other condensate. These condensates are withdrawn respectively through pipes 40 and 42. The uncondensed vapors discharged from condenser 8 are conducted through. a vapor line 44 into a fractionating tower 46 in which the vapors are passed through successively cooler bodies of reflux condensate iiowing downwardly through the tower. It is the object of the invention to condense substantially all of the higher boiling constituents in tower it so that only pressure distillate or gasoline materials will be conducted therefrom through valved vapor line @3. These vapors removed from chamber 46 through line 158 pass through heat exchanger 6 and water cooled condensers 50 and 52 in which substantially all of the gasoline constituents of the vapors are condensed. The cooled and condensed vapors and condensate discharged from` condenser 52 are conducted through a line 54 into a receiving tank 50 from which uncondensed gas is discharged through a pressure regulated relief line 58, while the cracked gasoline product is discharged through liquid level controlled outlet line 60.

1n order to maintain the desired outlet temperature in the tower A6 a portion of the condensate collected in receiver 50 may be withdrawn through a line 62 and forced by pump @It through a valve-controlled line 5t into the upper portion of tower 46. The quantity of product discharged through the line 66 is thermostatically controlled from the fluctuations in temperature in the upper portion of the tower 46 by means of the automatic valve operating mechanism 58 which is connected to a thermostat in tower 46 and to the valve in line 66. This mechanism may comprise any well-known apparatus commonly used for operating a valve in accordance with variations in temperature.

The reuX condensate discharged through the line lll is conducted through a connecting line I to a cooler I2 and then forced by means of pump 'I4 into the line 32 from which it is discharged into contact with the highly heated products passed from furnace I8. The quantity of condensate conducted from line 4l? to line 'I0 may be supplemented by condensate from line 42 by opening a valve 16, but any condensate not so used is discharged from line 42 through a valved pipe I8 into the lower portion of tower 45 where it is mingled with the reflux condensate produced and collected therein. This arrange ment insures the separation of the high boiling condensate having a relatively high carbon residue for passage back into the system without being conducted to the coils, whereas the condensate containing a relatively low carbon residue is discharged through line I8 into the lower portion of tower 45. Condenser 8 therefore segregates the high boiling point materials which may tend to cause coking if conducted through the coils of furnace I8.

The reflux condensate collected in the lower portion of the tower 4E is withdrawn therefrom through a line B0 and forced by means of a pump 82 under a pressure of about 1000 pounds per square inch intoo the line I5, in which it is mingled with the fresh charging stock, and conducted to furnace I8.

While the charging stock passed to the furnace coils in furnace I8 is under a pressure of about 1000 pounds per square inch, the pressure drop due to the coils in the furnace, will be about 250 pounds per square inch, so that the outlet pressure of the products in line 20 may be maintained at about '750 pounds per square inch. This pressure may be reduced at the point of the valve in line 20 to a pressure of about 250 pounds, which is maintained, except for necessary pressure drop, throughout the succeeding elements of the apparatus including chambers 24, 20, tower ri, the condensers` and receiver 56. Instead of reducing the pressure in line 2D it may be reduced at the valve in line 48.

The furnace I 8 is preferably of the flue gas recirculation type having the special details of construction in which the oil introduced from pipe l passes through a tube bank 84 mounted along the front wall of the combustion chamber, then through a tube bank BE mounted under the roof of the furnace in which the tubes run in opposite direction to that of the tubes in bank 84. These banks protect the front wall and roof from direct radiation. The products are then conducted from tube bank 86 into the lower portion of a third tube bank 8B mounted partly behind a bridge wall 90. The oil products are discharged from the upper tubes of the tube bank 83 directly into the transfer line 20. The bridge wall 90 is of relatively thin tile or other refractory material hung on or placed between certain of the tubes in the bank 88 so that part of the tubes of this bank are in the combustion chamber of the furnace.

The furnace is supplied with products of combustion from burners 92 in combustion tunnels 94 shown in Figs. 1 and 2. These products of combustion pass directly into the combustion chamber of the furnace and over the top of the bridge wall 00 then down over the tubes of bank 0&2 countercurrent to the flow of oil therethru. The tube banks 84 and 85 and a portion of the tubes of bank 88 receive radiant heat from. the products of combustion while the remainder of the tubes of bank 38 are heated by convection from the ue lgases passing over the top of bridge wall 00. The products of combustion discharged from tube bank 88 pass around the combustion tunnels E4 into an outlet iiue 96 shown in Fig. 2. A portion of the flue gases discharged from the furnace may be returned to a distributor flue 98 from which they are discharged into the furnace and mingled with the products of combustion from the burners. The return of flue gases to the front of the furnace provides a blanket of relatively cool gases passing up over` the tubes of bank 84 sothat these tubes are not directly washed by the hottest products of combustion as they discharge from the combustion tunnels 94. The method of heating provided by the furnace I8 is such that the oil introduced into tube bank 84 is quickly brought to a cracking temperature either in this bank or in bank E5, so that the tube bank 88 is substantially all used for giving the oil a time reaction which has been found advantageous in the transforming of straight run gasoline into a high anti-knock cracked product.

The plurality of lines are provided so that a transfer line will be available in case the one in use should become coked up.

Referring to the modified form of the invention shown in Fig. 3 of the drawings, the straight run gasoline or naphtha to be treated (which may have a boiling range of from 300 to 450 F.) is introduced into the system through a pipe 2 and pump 4. The gasoline introduced by the pump 4 is forced under a pressure of about 1000 pounds per square inch through a series of heat exchangers 6 and 8 by means of connecting pipes I0 and I2. From the heat exchanger 3 the gasoline which has now been heated to a temperature of from 500 to 600 F. is passed through a pipe I5 into a heating coil IE mounted in pipe still furnace i8. The gasoline passed into the coil I5 is gradually heated to a substantially high temperature until it reaches a maximum temperature of from 925 to 1100o F. in the radiant tube bank I9 mounted in the upper part of furnace I8. This heating at high temperature is continued for a sufficient time to transform a substantial portion of the saturated hydrocarbons present in the gasoline or naphtha, into unsaturated constituents which give the anti-knock property to the recovered product.

The highly heated gasoline material subjected -to "treatment in heating coils I6 and I9 is conductedfrom the latter coil through a pipe 2i) into the upper portion of an enlarged chamber 24 under a substantially reduced pressure regulated by a reducing Valve 2i in pipe 2D. The highly heated products conducted through pipe 22 are at such a high temperature that it has been found advantageous to reduce this temperature by the mixing of the products with an oil of substantially lower temperature, but of higher boiling vpoint than gasoline. In the present instance lfuel oil for example, is introduced through a valved pipe 25 directly into the transfer line 2i] between the pressure reducing valve 2l and the enlarged chamber 24. The mingled liquid and vapor products discharged into chamber 24 pass downwardly therethrough and leave the chamber together through one of a plurality of valved outlet lines 26 which connect directly with the lower portion of a second enlarged `chamber 28. Under certain circumstances, carbon or coke may be formed in the operation after the unit has been von stream for a long period of time, and accumulate in one of the lines 26 to such an extent as to cause the shutdown of the apparatus. In order to avoid this condition alternate emergency, draw-off lines 26 have been provided which connect the lower portion of chamber 24 with the lower portion of chamber 28.

Since the liquid and vapor products present in chamber 24 are withdrawn from the bottom thereof, it is apparent that no accumulation of liquid will be possible in this chamber, but all liquid will be transferred to chamber 26 in which a body thereof is maintained. If necessary the body of oil in chamber 28 may be maintained by the introduction of additional quantities of fuel oil `through a valved pipe 29 which connects with the fuel oil supply line 25. The vapors and liquid introduced into chamber 2S from chamber 24 are distributed substantially uniformly throughout the body of oil therein by means of an inclined distributor flange 3U mounted in chamber 28 Aabove the inlets of pipes 26.

Fuel oil vcracks at a temperature substantially below the temperature necessary for cracking such stocks as kerosene, and very materially below the temperature used for the transformation of 'gasoline in the present instance. It is the purpose therefore of the present invention to maintain a temperature of from '750 to about 825 F. in chamber 28 in order to effectively crack substantial portions of the fuel oil used as a quenching medium in transfer line '26 and chamber 24, or the fuel oil introduced into chamber 28 through line 29. Chamber 28 is provided with a valved residue withdrawal line 36 for the purpose of removing portions of the fuel oil to control the carbon content in chamber 23 and prevent substantial coking of the material therein, Suitable tests may be made on the contents of chamber 2S to determine the carbon content of the oil at various periods of the operation.

The mingled vapors separated in cracking chamber 28 comprise the transformed constituents of the gasoline charging stock and the cracked products resulting from the treatment of the fuel oil. These vapors are conducted from chamber 28 through a vapor line 38 into the lower portion of heat exchanger 8 in which the vapors pass in indirect heat exchange with the gasoline charging stock passing therethrough. This heat exchange produces a certain amount of condensation and reduces the temperature of the vapors from about 800 F. to about 675 F., at which temperature they are passed together with any condensate through a vapor line 44 into the lower portion of a fractionating tower 46. In the tower 46 the condensate introduced .through the pipe 44, as well as that formed in the tower, is collected as a body in the lower portion thereof which may be used as an accumulator.

The tower 46 may be the usual bubblercap type construction, but in the present instance it is preferably provided with an indirect heat exchange cooling system which includes a series of closed cooling coils 41 between the bubbler trays. A liquid cooling medium for the coils 41 preferably comprises a vhigh boiling point hydrocarbon such as fuel oil, which will not undergo substantial vaporization in the coils. This medium may be supplied from a tank 49 and conducted through a pipe 5I by means of a pump 53 and pipe 55 to the cooling coil 41 in the upper portion of Vtower 46. The cooling medium then passes downwardly in succession through the cooling coils and is finally removed from the lower portion of the tower through a pipe 51 and conducted through heat exchanger 6 inL indirect heat exchange with the gasoline stock being introduced into the system. The pump 53 is preferably operated automatically at a rate adapted to maintain the desired outlet temperature of vapors from tower 46 so that these vapors l comprise substantially all of the pressure distillate or composite gasoline product. In ordinary ope-ration, the temperature of the cooling medium leaving the tower through the pipe 51 will be somewhat below the temperature of the vapors introduced through pipe 44, but will be surliciently high to substantially preheat vthe gasoline charging stock passed through heat exchanger 6. The cooled fuel oil heat exchange medium is discharged into tank 49 from heat exchanger 6 through a line 59. If, in order to control the outlet temperature of vapors from tower 46, it is found necessary to use a cooling medium in the upper coils 41 which has a temperature above that normally used, the amount of fuel oil maintained in the closed system described above may be varied so as to maintain the supply in tank 49 at the proper temperature for use in the upper portion of tower 46.

The pressure distillate or composite product discharged as vapor from tower 46 is conducted through a valved vapor line 48 into a condenser 6l where the product is condensed under a pressure substantially equal to that maintained in chamber 28, except for the necessary pressure drop through the intervening elements of the apparatus. Condensation under this pressure, removes as liquid, substantially all of the constituents which may be utilized in a gasoline motor fuel, and permits the separation of a substantially dry gas comprising constituents having a boiling range of about that of propane or butane. condensate and uncondensed gases are conducted from condenser 6| through a pipe 54 into a product receiver 56 from which the condensate is removed through a valved pipe 60, and uncondensed gases through a valved lpipe '58.

Since the temperature of the vapors conducted through pipe 38 into heat exchanger 8 and tower 46 are substantially higher than the boiling points of certain gas oil and kerosene constituents, such materials present in the vapors are condensed in these elements of the apparatus and collected in the lower portion of the tower 46. Such material which is v-ery low in carbon residue content is removed from the accumulator in tower 4B through a valved pipe BEI and forced by means of pump 82 and a. pipe 83 under a pressure of about 1000 pounds per square inch into feed line I5 leading to furnace coil I5.

While the reflux material charged to the furnace I8 from tower 46 in Figs. 1 and 3 may crack at somewhat lower temperatures than that necessary for the transformation of the gasoline charging stock, the presence of the gasoline stock serves to prevent undue cracking of the higher boiling reflux material. In fact, it appears that a certain hydrogen exchange must occur between the gasoline material and the heavier reflux material in cracking coils, since in order to transform saturated hydrocarbons in the gasoline into unsaturated hydrocarbons, hydrogen must be removed, but without a substantial reduction in the hydrocarbon chain; whereas the hydrocarbon chain of the higher boiling reflux material is undoubtedly broken and the available hydrogen referred to utilized for partially saturating overly unsaturated products. The presence therefore of Imaterials of substantially the gas oil range in the coils at the temperatures employed does not cause coking as would ordinarily be the case. As an example of the type of chemical transformation which may occur in the cracking coils, it may be assumed that a gasoline constituent such as hexane may be dehydrogenated by the high temperature to produce hexylene and that a constituent of gas oil such as an unsaturated hydrocarbon containing lo carbons may be cracked to form two 8 carbon chain hydrocarbons, one or both of which may be doubly unsaturated (dienes). The hydrogen produced in the first instance would be preferentially used for partial saturation of the dienes produced from the gas oil.

The heat exchangers 5 and 8 shown diagrammatically in Figs. l and 3, are the usual high pressure heat exchangers in which the liquid passes through tubes in a double pass while the vapors pass around the tubes in indirect heat exchange with the liquid.

The pipe still furnace I8 in Fig. 3 is of usual construction in which the coil IE is a convection heating tube bank mounted behind a bridge wall, and coil I9 is a radiant heating tube bank which may comprise two or more superposed rows of tubes mounted above the convection tube bank and above the fire box. Heat may be supplied in the furnace IS by combustion of fuel oil or gas as in the usual practice.

Chambers 25 and 28 in Figs. 1 and 3 are preferably high pressure elements having a diameter of from 8 to l0 feet and a height of 3() to 5G feet. These two chambers are preferably connected at their upper ends by a valved pipe 8l which under the preferred method of operation is not used except for passage of vapors direct from chamber 2d into chamber 28 under an emergency. However. in starting up the apparatus, the vapors may be passed ldirectly through the line 8i until the temperature of the products leaving the furnace has been brought up to the desired cracking point. This will avoid condensation of relatively low boiling point constituents in the cool oil in chamber 28 which constituents would be later vaporized and passed t the final condenser without having been subjected to the desired transformation reaction,

The stock introduced into the system through pipe 25 (Fig. 3) while preferably comprising a fuel oil stock produced by straight distillation of crude oil, nevertheless, may comprise or include other materials such as gas oil. The stock here introduced however should have a boiling point higher than the desired gasoline product in order to avoid the presence of substantial amounts of untransformed material in the final product.

While the charging stock introduced through the line I is preferably under pressure of about 1G00 pounds per square inch, it is evident that the pressure at the outlet of coil I9 will be substantially lower or about 75() pounds per square inch, due to the pressure drop through the heating coils. In the preferred mode of operation the pressure is reduced by valve 2l to about 250 to 30) pounds per square inch, which pressure is maintained throughout the subsequent elements including chambers 24, 2B, heat exchanger 8, tower 46, condenser 6I and receiver 56, except for the necessary pressure drop through these elements. The pressure used on the cooling medium circulated through tower 46 is preferably as low as possible in order to avoid the use of expensive coils in this tower, but except for this element of expense the pressure may be raised to about 300 pounds per square inch, which will partially relieve the stress in heat exchanger and equalize the pressure between the vapors in tower 46 and the liquid in coils 41. Suitable pressure regulating means such as the valve in pipe 59 may be utilized for substantially equalizing the pressure in coils 41 and in tower 46.

In high temperature cracking operations as indicated above, certain amounts of dienes or other highly unsaturated compounds are formed which if left in the motor fuel product cause very substantial deposits of gum. The process of the present invention while employing very high temperatures of transformation, produces a composite product which is relatively free from gumforming constituents when compared with ordinary vapor phase cracked products where similar temperatures have been employed. This decrease in gum-forming constituents may be due in part to the chemical reactions suggested above, which undoubtedly take place to some extent in the cracking coils, but is further due to certain additional reactions which take place upon the mixing of the highly heated crack-ed product with the o-il stock in transfer line 20 and chambers 24 and Z8. This reaction apparently involves a certain amount of polymerization of gum-forming constituents which are either retained in the oil body in chamber 28 or removed with the reflux condensate in tower 46. The interaction between gum-forming constituents and the heavy hydrocarbon oils undoubtedly involves other reactions which are not known. In any case, the cornposite product produced by the process of the present invention is readily rei-ined by ordinary treating methods and does not have the gumforming tendencies usually found in motor fuel products produced by high temperature cracking. The gasoline charging stock used in the process o-f the present invention has a very low octane rating (about 40) and if used directly as a motor fuel in internal combustion engines now in use, will produce substantial knocking; whereas the composite product produced has a substantially high octane number (from '70 to 85) which may be used directly as an anti-knock motor fuel without the addition of anti-knock agents such as tetraethyl lead. l

Having thus described the invention in its preferred form, what is claimed as new is:

l. The process of increasing the octane rating of knock producing gasolines, which comprises preheating the gasoline to a temperature of about 550 F. under a pressure of about 1000 pounds per square inch, further heating the preheated gasoline while under said pressure to a temperature of from 925 to ll00 F. for a substantial period of time sulicient to convert a substantial portion of the saturated hydrocarbons present in said gasoline into unsaturated hydrocarbons, reducing the pressure on the highly heated gasoline and mingling therewith a substantially cooler oil having substantially no constituents as low boiling as the desired gasoline product, passing the resulting mixture into an enlarged Zone in which substantially no body of liquid is maintained, conducting' the mixture into a second enlarged Zone into intimate contact with an enlarged oil body maintained therein at a cracking temperature solely by the hot oil products introduced thereinto from said first enlarged zone, passing vapors from said second enlarged Zone in indirect heat exchange with said gasoline to effect said preheating, and further fractionating said vapors to separate a gasoline of relatively high octane rating compared to the initial gasoline stock.

2. The process of increasing the octane rating of gasolines of relatively low' octane number, which comprises forcing the gasoline to be treated through a series of heating Zones. under a pressure of about 1000 pounds per square inch and therein gradually heating the gasoline to a temperature of from 925 to 1050 F., maintaining the highly heated gasoline constituents at approximately said temperature while passing the same through a long heated reaction coil in which the gasoline is heated for a substantial period of time suclentto convert a substantial portion of the saturated hydrocarbons present in said gasoline into unsaturated hydrocarbons, reducing the pressure on the highly heated gasoline product to about 250 pounds per square inch and passing it into intimate contact with a relatively cooler oil of substantially higher boiling point, separating vapors from unvaporized oil constituents, cooling the separated vapors by passing them in indirect heat exchange with gasoline charging stock, and thereafter separating the desired gasoline of high octane number from higher boiling constituents in the remaining vapors.

3. The process of raising the octane number of gasolines, which comprises passing the gasoline to be treated in a coniined stream through a heatingzone under a pressure of about 1000 pounds per square inch, heating the gasoline of said stream to a temperature of about 975 F., maintaining the gasoline at approximately said temperature in a heating coil for a substantial period of time suilicient to convert a substantial portion of the saturated hydrocarbons present in said gasoline into unsaturated hydrocarbons, reducing the pressure on the resulting highly heated products and mixing them with a relatively cooler oil thereby substantially reducing their temperature, separating vapors from unvaporized oil constituents of the resulting mixture, and passing the vapors into a fractionating Zone through which a high boiling point cooling medium is circulated in a closed cycle in indirect heat exchange with vapors, said cycle also including the passage of the cooling medium heated by the heat exchange with said vapors in indirect heat exchange with said gasoline being passed to said heating zone, the gasoline in said heat exchange being at a pressure of about 1000 pounds per square inch.

4. The process of increasing the octane rating of knock-producing gasolines, which comprises' passing the knock-producing gasoline in a conned stream of restricted cross-section through a heating zone and therein rapidly heating the gasoline to a high cracking temperature of from 925 to 1100 F., at a superatmospheric pressure of from '750 to 1000 pounds per square inch, continuing the heating of the conined stream of gasoline in` a subsequent heating zone of restricted cross-section at substantially the temperature attained in said first-mentioned Zone whereby a substantial time is allowed for conversion of said gasoline, said time being suiicient to convert a substantial portion of the saturated hydrocarbons present in said gasoline into unsaturated hydrocarbons, conducting the highly heated gasoline products from said heating into the upper portion of an enlarged vertical Zone in which no substantial body of liquid oil is maintained and in which the gasoline products are substantially all in vapor phase, passing the gasoline constituents downwardly through said Zone thereby permitting further conversion of the gasoline constituents at a relatively high temperature, mingling a relatively cool cil with the products passed through said chamber, and conducting the resulting mixture into intimate contact with an enlarged body of oil maintained in a second enlarged zone, and thereafter recovering a highly cracked gasoline product from the vapors resulting from the cracking operation.

5. The process of transforming a gasoline of low octane number into a gasoline of high octane number, which comprises forcing the gasoline to be transformed in a conined stream'v through a heating zone at a pressure of about 1000 pounds per square inch, heating the gasoline in` said zone to a high temperature of from 925 to 1050io F. adapted to transform substantial proportions of the saturated hydrocarbons present in the gasoline into unsaturated hydrocarbons, continuing the heating of the gasoline constituents while passing the same in a stream of restricted cross section through a highly heated reaction` coil in which the gasoline is heated for a substantial period of time sufficient to convert a substantial portion of the saturated hydrocarbons present in said gasoline into unsaturated hydrocarbons, reducing the pressure on the highly heated products leaving said reaction coil to a pressure of about 250 pounds per square inch, passing the resulting highly heated products from the reaction coil into the upper portion of a tall vertical enlarged reaction zone in which there is no substantial body of oil and passing the products downwardly therethrough, and substantially cooling the products while at said reduced pressure in the lower portion of said enlarged reaction zone by intimately mingling therewith a relatively cooler hydrocarbon oil yor" higher boiling point than gasoline.

DAVID G. BRANDT. 

